1. Field of the Invention
The present invention relates to a process for removing volatile components in a polyarylene sulfide resin in the production of the polyarylene sulfide resin. More particularly, it pertains to a process for removing volatile components in a polyarylene sulfide resin which process is capable of steadily and economically removing volatile components in the polyarylene sulfide resin well suited for use in electrical parts, electronic parts and highly rigid materials by means of a simple and convenient installation without necessitating expensive machinery or equipment such as a dryer, and further enables a long-term continuous running.
2. Description of the Related Arts
In the production of a polyarylene sulfide (hereinafter sometimes referred to as “PAS”) resin, it has been contrived to enhance a cleaning efficiency and simplify the production process by directly cleaning a polymerization reaction mixture at a high temperature for a PAS resin which is produced by subjecting a sulfur source and a dihalogenated aromatic compound to polymerization reaction. However in the above-mentioned case, a large amount of volatile components are contained in a solution of a PAS resin in a molten state in an organic solvent which solution is separated after the cleaning of the polymerization reaction mixture for a PAS resin, whereby it is made necessary to remove the volatile components as mentioned above in order to produce a high quality PAS resin. The volatile components have heretofore been removed by cleaning and drying granulated PAS resin, but the method is involved in such a problem as requiring a large amount of cleaning water and at the same time, expensive machinery and equipment such as a dryer.
As a countermeasure against the aforesaid problem, U.S. Pat. No. 3,707,528 discloses that a PAS resin containing a minimized amount of impurities can simply and conveniently be produced by flashing a polymerization reaction slurry liquid for PAS resin so as to recover the volatile components. In addition, Japanese Patent Application Laid-Open No. 290376/2000 (Heisei 12) discloses a process for removing volatile components in a PAS resin which contains an aprotic organic solvent separated from polymerization reaction mixture for a PAS resin by the use of an extruder.
However, the above-cited U.S. Pat. No. 3,707,528 is involved in such a problem that a long retention time of the PAS resin in a flash drum sometimes gives rise to deterioration of the polymer therein, and the resultant deteriorated product plugs up the outlet of the drum, and the like problem. The above-cited Japanese Patent Application Laid-Open No. 290376/2000 is involved in such a problem that the volatile components are accompanied with a PAS resin, which adheres to the opening portion of a vent to plug up the opening portion at the time of degassing, hence deteriorating the performance of removing volatile components. The above-mentioned tendency is particularly remarkable in the case of a PAS resin having a low molecular weight, thereby making it impossible to carry out a long-term continuous running.